Deadly Invasion

Divers in the waters of the western Atlantic are on a killing spree. Armed with spears and containment devices, they take to the water in order to cull as much as possible. Tournaments are held with cash prizes awarded for the biggest, smallest and heaviest haul. There is one specific species targeted, but no discrimination between age, size or gender. Environmentalists, scientists and even governments actively support the culling. But exactly what are they hunting and why?

The target is the lionfish and the reason they are being culled with such ferocity is due to the devastation they are inflicting on a beautiful habitat. Such is their appetite, that their stomach can stretch up to thirty times to accommodate prey over half their own size. A study in the Bahamas found them to cause an 80 percent reduction in native fish in just five weeks. They breed and spread at an astonishing rate and have been found to hold up to 60 dead fish and crustaceans in their gut at one time. Native species now struggle as they compete with this newcomer, and immense strain is being put on the food chain. Simply put, the lionfish are literally eating the reef population in to extinction.

The problem stems from the fact that these fish are not native to the east coast of America. Their arrival has caused chaos within this ecosystem. Lionfish are referred to as an “invasive species” due to the fact that, since their introduction in the mid 1980’s, their population has simply exploded. They have found a utopia in this new habitat as they feed gluttonously without the threat of any natural predators. Dr. James Morris from the National Oceanic and Atmospheric Administration (NOAA) has said that: “Lionfish may prove to be one of the greatest threats of this century to tropical Atlantic reefs.”

The exact story behind how they arrived in the Americas is unknown, but there has been much speculation. A popular theory was that an ocean front aquarium containing lionfish was damaged in 1992 during hurricane Andrew causing its contents to spill in to the sea. While this may well have happened, it cannot be the sole cause of the problem as the first reported sighting in Florida, USA, 1985 predates the hurricane. Scientists believe that the earliest recorded sightings were of fish that were released in to the ocean by private aquarium owners. It is also believed that the present situation results from multiple releases as opposed to one careless owner.

To call the lionfish invasive as a species is, I think, unfair. These fish made no conscious decision to uproot themselves from their native waters and venture in to new territories with grand plans of domination. The truth is that they are more a victim of their own extraordinary beauty. Lionfish have a unique, majestic appearance that, unfortunately for them, makes for a good commodity in the aquarium trade. It is this attraction that has resulted in them being plucked from their indigenous Indo-Pacific seas. Aquarium owners who bought lionfish have been known to struggle to keep up with the demands of their appetite. In these cases instead of killing them or rehoming them in another aquarium, they were dumped in the ocean.

Divers who have been lucky enough to encounter the lionfish in both their Asian and American habitats have noticed that there are differences between old and new. A common observation is that the new arrivals are much bigger in size than their cousins in their natural habitat. Their behaviour is also different; they are far less timid than their relatives, due to the absence of any kind of threat from other marine life, and they congregate in larger groups. Photographers notice that the more defensive lionfish in Asia will point their venom-filled dorsal spines at anyone who gets too close, a survival instinct that is far less common in their Atlantic relatives.

What is incredible about this translocation is the speed at which this species has conquered such a huge amount of territory. Since the first recording in Florida, lionfish have now been reported as far north as New York and as far south as Venezuela. They spread at such an alarming rate because the females are capable of releasing up to 30,000 eggs every 4 days. The egg sacks float in the water columns, where currents transport them to their new location. Previously uninvaded reef areas become affected when the current washes large numbers of eggs on to them starting a population boom.

They are a very versatile species, having the ability to live just below the surface or even at depths as great as 175 meters.

Attempts have been made to incorporate this voracious carnivore in to the existing food chain, but so far there has been little success. Hunters have tried spearing the fish and then feeding them to predators such as snappers, groupers, moray eels and sharks, who happily eat the dead or dying lionfish from a spear, but very rarely will actually attack or kill the lionfish. In Grand Cayman for example, feeding lionfish to other species has now been banned. Having tried this as a potential solution it was found that it only contributed towards the unbalance, as predators started to associate divers with food. Reports of moray eels swimming towards divers (often causing panic attacks) are one example of a negative impact on diver safety. Changes in the behaviour of fish such as groupers and snappers have been observed, for example in their closer proximity to divers who could be hunting illegally. These are just a couple of reasons why the Department of Environment concluded that feeding was not the answer.

As nature struggles to adjust to yet another blow from human intervention, there does not appear to be an overall solution in sight. Ideas along the lines of importing more species from Asia who already feed on lionfish have been written off as too risky. One lionfish culler jokingly suggested starting a rumour that lionfish are an aphrodisiac that stimulate weight loss.

In a desperate attempt to suppress the population growth, local communities are promoting the hunting and killing of both kinds of invasive lionfish – pterois volitans and pterois miles. Mass fishing techniques are not possible due to their inhabiting confined spaces like small tunnels or space under ledges. Currently, the most effective way to remove lionfish from the reef is for divers to spear them.

There is a misconception that lionfish are poisonous but in truth the white meat is perfectly edible. They are equipped with venomous spines which they have to defend themselves but once removed, the fish is very good to eat. As the lionfish venom is not heat stable, when subjected to high temperatures it is even possible to make dishes with the spines on creating quite a dramatic visual effect on the plate.

Lionfish culling has become a very popular activity throughout the tropical western Atlantic. Some kill the fish to eat, others to sell, some to try to offer relief to the struggling reefs, and then of course there are the gung-ho chest beaters who just want to kill something. Innovative entrepreneurs have established tradelines with companies specializing in catching, killing and exporting the fish to fine dining restaurants in the States. Lionfish now appear on menus throughout most of the Caribbean with specialities that range from lionfish ceviche to some very authentic tasting lionfish and chips. Many dive centres are actively assisting in the culling activities by providing spearfishing training and education. Cullers are made aware of how to hunt safely and responsibly in order to avoid injury to themselves or their surroundings. While on Caribbean holidays, divers can be trained in the use of spear guns, Hawaiian slings or even nets to catch the fish and then how to safely remove the spines before handing them over to the kitchen.

Culling lionfish is a risky business, being stung or “spiked” by a lionfish spine is not something to be brushed off. The venom causes intense pain and swelling and can cause necrosis of the flesh or even send the recipient in to anaphylactic shock. Most injuries are sustained to the divers hands and often occur when trying to put a lionfish in to a containment device underwater or when handling the dead fish back on land.

No -one knows yet how this story will unfold. It is speculated that we have not yet seen the worst of the invasion, and it is believed that their population will continue to rise. As the footprint of the lionfish upon the reef gets deeper, so the struggle becomes harder for native marine life. It is hoped that controlling species will develop a taste for lionfish but until such time the dive community accepts the responsibility to do what it can to keep numbers as low as possible. For now, the advice is to eat our way through this and given the taste of some of the fine dishes being cooked up, I for one am more than happy to do my bit.

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2 thoughts on “Deadly Invasion”

Having gone through the culling license process for the Cayman Islands, I would think there could be an easier method to invite additional cullers. But I’m definitely happy to do my part and I had a great instructor!

And since the likelihood of removing the species is probably non-existent given their proliferation, it would be an interesting study to determine what level of predation (by humans) would be needed to support a healthy reef. I suspect the biggest challenge to achieve the level of predation would be the depth required to be reached by cullers to be effective.

Recently we have seen a couple of cases of local wildlife eating lionfish without any human assistance. I feel that human activity like culling is not a solution in itself, merely a way of slowing the problem down until hopefully, habits of existing predators develop. It would be interesting to know how much human activity would be needed to support a healthy reef, I guess it would depend on the size of the reef, i.e. a section of Grand Cayman or it’s entire coral population.